The present invention relates to an electrically controlled, decentralized control system in a vehicle, for example, a braking system.
In the case of such control systems, which are generally not equipped with a mechanical, hydraulic or pneumatic backup system that ensures the functioning of the control system in the case of a fault, special attention must be placed on availability, even in the event of a fault. An example for an electrically controlled, decentralized, braking system which satisfactorily meets the demands placed is described in German Patent No. 196 34 567 (GB 2 316 726 B). This known braking system for a motor vehicle (brake-by-wire) has a decentralized design and is made of various control modules, at least one control module for ascertaining the driver""s braking input (desire) and control modules, allocated to individual vehicle wheels, for adjusting the braking force. In addition, to ensure the energy supply, two energy sources or vehicle electrical systems are provided which are independent of one another. To guarantee that the control system is at least partially operable, even in the event one of these energy sources or vehicle electrical systems fails, provision is made to power the central control module for ascertaining the driver""s input from both energy sources, and to allocate the control modules for adjusting the braking force either to one or the other energy source, this allocation being carried out in such a way that, if the one energy source fails, at least a part of the wheel brakes remains operable. In this context, the allocation of the energy sources to the individual elements is permanent, the allocation of the high-current loads (e.g., actuators of the wheel brakes) to the energy sources not being addressed.
A solution for the last-named problem can be gathered from German Patent No. 195 37 464. A decentralized braking system is proposed there, as well, in which at least two energy sources are provided that are independent of one another. To ensure the operability of the braking system in the event one of these energy sources fails, a first group of wheel-brake actuators is allocated to the first energy source, and a second group of wheel-brake actuators is allocated to the second energy source. The energy sources are permanently wired to the elements to be powered in this case, as well.
The permanent wiring for the energy distribution, known from the related art, restricts the flexibility of the system, particularly if an energy source fails.
Therefore, an object of the present invention is to improve the distribution of energy in an electrically controlled, decentralized control system in a vehicle.
A separation is made between the energy supply of the high-current loads (actuators and power output stages) and the control units, the control units advantageously being decoupled from line-conducted disturbances and voltage drops on the energy line which are caused by the power electronics of the high-current loads.
In an advantageous manner, a permanent wiring of the high-current loads is provided, while the control units and low-current loads (e.g., retaining brake) are switched via a central switching element. This central switching element is connected to both energy sources, so that if one of the energy sources fails, the energy supply of the control units can advantageously be switched over to a different energy circuit. In this manner, an energy redundance is provided, availability of the control system is increased and flexibility is expanded.
Due to the separation of the energy supply of the high-current loads and of the control units and low-current loads, respectively, if the power unit or a connected energy path fails, the control unit advantageously remains fully functional. Therefore, it can be utilized for further evaluation of sensor signals, for monitoring the overall system and/or for activation or energy supply of low-current loads, e.g., a retaining brake.
The energy distribution, described in the following, advantageously allows a separation of each individual element from the energy supply when this element exhibits or is causing faulty conditions.
In a braking system, a retaining brake must continue to be able to be actuated if one of the energy circuits fails. This is necessary in a braking system in order to release an applied actuator.
It is particularly advantageous that a computer-controlled switch-on and/or switch-off strategy of the overall system can be provided which is simple to implement. In this context, for example, an after-run is established to allow the execution of functions such as clearance (air gap) adjustment, data protection, etc., until the final switch-off. Upon switching on, a central switching element connecting the energy supply allows a time-synchronous, controlled switch-on of the control units.
Advantageously, this energy distribution is used not only in the case of the preferred exemplary embodiment of a decentralized braking system, but also for other decentralized control systems in the field of vehicle technology, such as steering systems and actuating systems having, for example, a plurality of electromotors, or for internal combustion engines having at least two independent cylinder banks, etc.